Methods of Plugging and Abandoning a Well Using Compositions Comprising Cement Kiln Dust and Pumicite

ABSTRACT

The present invention is directed to plug-and-abandon operations that use plugging compositions comprising cement kiln dust, pumicite, and/or lime. An embodiment includes a method of plugging a well bore for abandonment comprising: placing a plugging composition in the well bore, the plugging composition comprising: cement kiln dust in an amount of about 5% to about 100% by weight of cementitious components, pumicite in an amount of about 5% to about 100% by weight of cementitious components, 0% to about 24% of Portland cement by weight of cementitious components, and water; and allowing the plugging composition to set and form a plug.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of co-pending U.S. patentapplication Ser. No. 12/606,381, entitled “Methods of CementingSubterranean Formation Formations Using Cement Kiln Dust in CompositionsHaving Reduced Portland Cement Content,” filed on Oct. 27, 2009, whichis a continuation in part of U.S. application Ser. No. 12/420,630,issued as U.S. Pat. No. 7,631,692, entitled “Settable CompositionsComprising a Natural Pozzolan and Associated Methods,” filed on Apr. 8,2009, which is a continuation in part of U.S. patent application Ser.No. 12/349,676, issued as U.S. Pat. No. 7,674,332, entitled “ExtendedSettable Compositions Comprising Cement Kiln Dust and AssociatedMethods,” filed on Jan. 7, 2009, which is a divisional of U.S. patentapplication Ser. No. 12/034,886, issued as U.S. Pat. No. 7,478,675,entitled “Extended Settable Compositions Comprising Cement Kiln Dust andAssociated Methods, filed on Feb. 21, 2008, which is a continuation inpart of U.S. patent application Ser. No. 11/223,669, issued as U.S. Pat.No. 7,445,669, entitled “Settable Compositions Comprising Cement KilnDust and Additive(s),” filed Sep. 9, 2005, the entire disclosures ofwhich are incorporated herein by reference.

BACKGROUND

The present invention relates to cementing operations and, moreparticularly, in certain embodiments, to plug-and-abandon operationsusing plugging compositions comprising cement kiln dust (“CKD”),pumicite, and/or lime.

In cementing methods, such as well construction and remedial cementing,sealant compositions are commonly utilized. As used herein, the term“sealant composition” refers to a composition(s) that hydraulically setsor otherwise develops compressive strength suitable for use insubterranean applications. One type of a sealant composition is aplugging composition that can be used in plug-and-abandon operationswhereby a plug is formed in a well bore to seal off the well bore forabandonment. In performing plug-and-abandon operations, a pluggingcomposition may be placed in the well bore at a desired depth. Theplugging composition should set in the wellbore, forming a hardened mass(e.g., a plug) that seals of selected intervals of the well bore. Theplug should prevent and/or reduce zonal communication and migration offluids that may contaminate water-containing formations. It maydesirable in certain instances to form one or more plugs in the wellbore adjacent to hydrocarbon-producing formations and water-containingformations.

Sealant compositions used heretofore may comprise Portland cement.Portland cement generally is a major component of the cost for thesealant compositions. To reduce the cost of such sealant compositions,other components may be included in the sealant composition to replacesome of the Portland cement. Such components may include cement kilndust (“CKD”), fly ash, slag cement, shale, metakaolin, zeolite, and thelike. CKD is a partially calcined kiln feed which is removed from thegas stream and collected, for example, in a dust collector during themanufacture of cement. The term “CKD” is used herein to mean cement kilndust made as described above and equivalent forms of cement kiln dustmade in other ways.

SUMMARY

The present invention relates to cementing operations and, moreparticularly, in certain embodiments, to plug-and-abandon operationsusing plugging compositions comprising CM), pumicite, and/or lime.

An embodiment of the present invention provides a method of plugging awell bore for abandonment comprising: placing a plugging composition inthe well bore, the plugging composition comprising cement kiln dust inan amount of about 5% to about 100% by weight of cementitiouscomponents, pumicite in an amount of about 5% to about 100% by weight ofcementitious components, 0% to about 24% of Portland cement by weight ofcementitious components, and water; and allowing the pluggingcomposition to set and form a plug.

Another embodiment of the present invention provides a method ofplugging a well bore for abandonment comprising: placing a pluggingcomposition in the well bore, the plugging composition comprising: acementitious component consisting essentially of cement kiln dust,pumicite, and lime, and water; and allowing the plugging composition toset and form a plug.

Yet another embodiment of the present invention provides a pluggingcomposition comprising: cement kiln dust in an amount of about 5% toabout 100% by weight of cementitious components; pumicite in an amountof about 5% to about 100% by weight of cementitious components; 0% toabout 24% of Portland cement by weight of cementitious components; andwater.

The features and advantages of the present invention will be readilyapparent to those skilled in the art. While numerous changes may be madeby those skilled in the art, such changes are within the spirit of theinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to cementing operations and, moreparticularly, in certain embodiments, to plug-and-abandon operationsusing plugging compositions comprising CKD, pumicite, and/or lime. Theremay be several potential advantages to the methods and compositions ofthe present invention, only some of which may be alluded to herein. Oneof the many potential advantages of embodiments of the present inventionis that the inclusion of the CKD and/or pumicite in the pluggingcomposition may reduce the amount of, or potentially eliminate, a highercost additive, such as Portland cement, resulting in a more economicalplugging composition. Another potential advantage of embodiments of thepresent invention is that reduction of the amount of Portland cementshould reduce the carbon footprint of the plug-and-abandon operation.

Embodiments of the plugging compositions of the present invention maycomprise CKD, pumicite, and water. In an embodiment, the pluggingcompositions may further comprise lime. In one particular embodiment,the plugging composition comprises a cementitious component thatconsists essentially of CKD, pumicite, and lime. Other optionaladditives may also be included in embodiments of the pluggingcompositions of the present invention as desired, including, but notlimited to, fly ash, slag cement, metakaolin, shale, zeolite,combinations thereof, and the like. As described in more detail herein,embodiments of the plugging compositions of the present invention may befoamed and/or extended as desired by those of ordinary skill in the art.

The plugging compositions of the present invention should have a densitysuitable for a particular application as desired by those of ordinaryskill in the art, with the benefit of this disclosure. In someembodiments, the plugging compositions of the present invention may havea density in the range of from about 8 pounds per gallon (“ppg”) toabout 16 ppg. In other embodiments, the plugging compositions may befoamed to a density in the range of from about 8 ppg to about 13 ppg.

Embodiments of the plugging compositions generally may comprise CKD.During the manufacture of cement, a waste material commonly referred toas cement kiln dust (“CKD”) is generated. Disposal of the waste CKD canadd undesirable costs to the manufacture of the cement, as well as theenvironmental concerns associated with its disposal. The chemicalanalysis of CKD from various cement manufactures varies depending on anumber of factors, including the particular kiln feed, the efficienciesof the cement production operation, and the associated dust collectionsystems. CKD generally may comprise a variety of oxides, such as SiO₂,Al₂O₃, Fe₂O₃, CaO, MgO, SO₃, Na₂O, and K₂O.

The CKD generally may exhibit cementitious properties, in that it mayset and harden in the presence of water. In accordance with embodimentsof the present invention, the CKD may be used, among other things, toreplace higher cost cementitious components, such as Portland cement,resulting in more economical plugging compositions. In addition,substitution of the CKD for the Portland cement should result in aplugging composition with a reduced carbon footprint.

The CKD may be included in the plugging compositions in an amountsufficient to provide the desired compressive strength, density, costreduction, and/or reduced carbon footprint. In some embodiments, the CKDmay be present in the plugging compositions of the present invention inan amount in the range of from about 1% to about 100% by weight ofcementitious components. Cementitious components include thosecomponents or combinations of components of the plugging compositionsthat hydraulically set, or otherwise harden, to develop compressivestrength, including, for example, CKD, fly ash, pumicite, slag, lime,shale, and the like. The CKD may be present, in certain embodiments, inan amount of about 5%, about 10%, about 15%, about 20%, about 25%, about30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%,about 65%, about 70%, about 75%, about 80%, about 90%, or about 95%. Inone embodiment, the CKD may be present in the plugging compositions ofthe present invention in an amount in the range of from about 5% toabout 99% by weight of cementitious components. In another embodiment,the CKD may be present in an amount in the range of from about 5% toabout 80% by weight of cementitious components. In yet anotherembodiment, the CKD may be present in an amount in the range of fromabout 50% to about 80% by weight of cementitious components. One ofordinary skill in the art, with the benefit of this disclosure, willrecognize the appropriate amount of CKD to include for a chosenapplication.

Embodiments of the plugging compositions further may comprise pumicite.Generally, pumicite is a volcanic rock that exhibits cementitiousproperties, in that it may set and harden in the presence of hydratedlime and water. Hydrated lime may be used in combination with thepumicite, for example, to provide sufficient calcium ions for pumiciteto set. In accordance with embodiments of the present invention, thepumicite may be used, among other things, to replace higher costcementitious components, such as Portland cement, resulting in moreeconomical plugging compositions. As previously mentioned, replacementof the Portland cement should also result in a plugging composition witha reduced carbon footprint.

Where present, the pumicite may be included in an amount sufficient toprovide the desired compressive strength, density, cost reduction and/orreduced carbon footprint for a particular application. In someembodiments, the pumicite may be present in the plugging compositions ofthe present invention in an amount in the range of from about 1% toabout 100% by weight of cementitious components. For example, thepumicite may be present in an amount of about 5%, about 10%, about 15%,about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%,about 90%, or about 95%. In one embodiment, the pumicite may be presentin the plugging compositions of the present invention in an amount inthe range of from about 5% to about 99% by weight of cementitiouscomponents. In another embodiment, the pumicite may be present in anamount in the range of from about 5% to about 80% by weight ofcementitious components. In yet another embodiment, the pumicite may bepresent in an amount in the range of from about 10% to about 50% byweight of cementitious components. In yet another embodiment, thepumicite may be present in an amount in the range of from about 25% toabout 50% by weight of cementitious components. One of ordinary skill inthe art, with the benefit of this disclosure, will recognize theappropriate amount of the natural pozzolan to include for a chosenapplication.

The water that may be used in embodiments of the plugging compositionsinclude, for example, freshwater, saltwater (e.g., water containing oneor more salts dissolved therein), brine (e.g., saturated saltwaterproduced from subterranean formations), seawater, or combinationsthereof. Generally, the water may be from any source, provided that thewater does not contain an excess of compounds that may undesirablyaffect other components in the plugging composition. In someembodiments, the water may be included in an amount sufficient to form apumpable slurry. In some embodiments, the water may be included in theplugging compositions of the present invention in an amount in the rangeof about 40% to about 200% by weight of cementitious components. In someembodiments, the water may be included in an amount in the range ofabout 40% to about 150% by weight of cementitious components. One ofordinary skill in the art, with the benefit of this disclosure, willrecognize the appropriate amount of water to include for a chosenapplication.

Embodiments of the plugging compositions further may comprise lime. Incertain embodiments, the lime may be hydrated lime. The lime may beincluded in embodiments of the plugging compositions, for example to,form a hydraulic composition with other components of the pluggingcompositions, such as the pumicite, fly ash, slag, and/or shale. Wherepresent, the lime may be included in the plugging compositions in anamount sufficient for a particular application. In some embodiments, thelime may be present in an amount in the range of from about 1% to about40% by weight of cementitious components. For example, the lime may bepresent in an amount of about 5%, about 10%, about 15%, about 20%, about25%, about 30%, or about 35%. In one embodiment, the lime may be presentin an amount in the range of from about 5% to about 20% by weight ofcementitious components. One of ordinary skill in the art, with thebenefit of this disclosure, will recognize the appropriate amount of thelime to include for a chosen application.

In an embodiment, plugging compositions of the present invention maycomprise pumicite and CKD in a weight ratio of from about 1/99 to about99/1 with lime present in an amount of from about 5% to about 15% by thecombined weight of the pumicite and the CKD. In another embodiment,plugging compositions of the present invention may comprise pumicite andCKD in a weight ratio of from about 65/35 to about 80/20 with limepresent in an amount of from about 5% to about 15% by the combinedweight of the pumicite and the CKD. In general, it should be understoodthat as the amount of the CKD is decreased the amount of the pumicitemay be increased, in accordance with embodiments of the presentinvention.

It should be understood that use of Portland cement in embodiments ofthe plugging compositions should be reduced or even eliminated toprovide, for example, the desired cost savings and/or reduced carbonfootprint. Accordingly, embodiments of the plugging compositions of thepresent invention may comprise Portland cement in an amount of 0% toabout 24%. For example, the Portland cement may be present in an amountof about 1%, 5%, about 10%, about 15%, or about 20%. In an embodiment,the Portland cement may be present in an amount in the range of fromabout 0% to about 20%. In another embodiment, the Portland cement may bepresent in an amount in the range of from about 0% to about 10%. In yetanother embodiment, the plugging compositions may be essentially free ofPortland cement. As used herein, the term “essentially free” means lessthan about 1% by weight of cementitious components. In certainembodiments, the plugging composition may contain Portland cement in anamount less than about 0.1% by weight of cementitious components and,alternatively, less than about 0.01% by weight of cementitiouscomponents. By way of example, the plugging composition, in certainembodiments, may be free of Portland cement, in that the pluggingcomposition contains no Portland cement.

The Portland cements include those classified as Classes A, C, G, and Hcements according to American Petroleum Institute, API Specification forMaterials and Testing for Well Cements, API Specification 10, Fifth Ed.,Jul. 1, 1990. In addition, the Portland cements include those classifiedas ASTM Type I, II, or III.

Embodiments of the plugging compositions further may comprise fly ash. Avariety of fly ashes may be suitable, including fly ash classified asClass C and Class F fly ash according to American Petroleum Institute,API Specification for Materials and Testing for Well Cements, APISpecification 10, Fifth Ed., Jul. 1, 1990. Class C fly ash comprisesboth silica and lime so that, when mixed with water, it should set toform a hardened mass. Class F fly ash generally does not containsufficient lime, so an additional source of calcium ions is required forthe Class F fly ash to form a hydraulic composition. In someembodiments, lime may be mixed with Class F fly ash in an amount in therange of about 0.1% to about 25% by weight of the fly ash. In someinstances, the lime may be hydrated lime. Suitable examples of fly ashinclude, but are not limited to, POZMIX® A cement additive, commerciallyavailable from Halliburton Energy Services, Inc., Duncan, Okla.

Where present, the fly ash generally may be included in the pluggingcompositions in an amount sufficient to provide the desired compressivestrength, density, and/or cost. In some embodiments, the fly ash may bepresent in the plugging compositions of the present invention in anamount in the range of about 5% to about 75% by weight of cementitiouscomponents. In some embodiments, the fly ash may be present in an amountin the range of about 10% to about 60% by weight of cementitiouscomponents. One of ordinary skill in the art, with the benefit of thisdisclosure, will recognize the appropriate amount of the fly ash toinclude for a chosen application.

Embodiments of the plugging compositions further may comprise a slagcement. In some embodiments, a slag cement that may be suitable for usemay comprise slag. Slag generally does not contain sufficient basicmaterial, so slag cement further may comprise a base to produce ahydraulic composition that may react with water to set to form ahardened mass. Examples of suitable sources of bases include, but arenot limited to, sodium hydroxide, sodium bicarbonate, sodium carbonate,lime, and combinations thereof.

Where present, the slag cement generally may be included in the pluggingcompositions in an amount sufficient to provide the desired compressivestrength, density, and/or cost. In some embodiments, the slag cement maybe present in the plugging compositions of the present invention in anamount in the range of about 0.1% to about 99% by weight of cementitiouscomponents. In some embodiments, the slag cement may be present in anamount in the range of about 5% to about 75% by weight of cementitiouscomponents. One of ordinary skill in the art, with the benefit of thisdisclosure, will recognize the appropriate amount of the slag cement toinclude for a chosen application.

Embodiments of the plugging compositions further may comprisemetakaolin. Generally, metakaolin is a white pozzolan that may beprepared by heating kaolin clay, for example, to temperatures in therange of about 600° C. to about 800° C. In some embodiments, themetakaolin may be present in the plugging compositions of the presentinvention in an amount in the range of about 5% to about 95% by weightof cementitious components. In some embodiments, the metakaolin may bepresent in an amount in the range of about 10% to about 50% by weight ofcementitious components. One of ordinary skill in the art, with thebenefit of this disclosure, will recognize the appropriate amount of themetakaolin to include for a chosen application.

Embodiments of the plugging compositions further may comprise shale.Among other things, shale included in the plugging compositions mayreact with excess lime to form a suitable cementing material, forexample, calcium silicate hydrate. A variety of shales may be suitable,including those comprising silicon, aluminum, calcium, and/or magnesium.An example of a suitable shale comprises vitrified shale. Suitableexamples of vitrified shale include, but are not limited to,PRESSUR-SEAL FINE LCM material and PRESSUR-SEAL COARSE LCM material,which are commercially available from TXI Energy Services, Inc.,Houston, Tex. Generally, the shale may have any particle sizedistribution as desired for a particular application. In certainembodiments, the shale may have a particle size distribution in therange of about 37 micrometers to about 4,750 micrometers.

Where present, the shale may be included in the plugging compositions ofthe present invention in an amount sufficient to provide the desiredcompressive strength, density, and/or cost. In some embodiments, theshale may be present in the plugging compositions of the presentinvention in an amount in the range of about 5% to about 75% by weightof cementitious components. In some embodiments, the shale may bepresent in an amount in the range of about 10% to about 35% by weight ofcementitious components. One of ordinary skill in the art, with thebenefit of this disclosure, will recognize the appropriate amount of theshale to include for a chosen application.

Embodiments of the plugging compositions further may comprise zeolite.Zeolites generally are porous alumino-silicate minerals that may beeither a natural or synthetic material. Synthetic zeolites are based onthe same type of structural cell as natural zeolites, and may comprisealuminosilicate hydrates. As used herein, the term “zeolite” refers toall natural and synthetic forms of zeolite. Examples of suitablezeolites are described in more detail in U.S. Pat. No. 7,445,669. Anexample of a suitable source of zeolite is available from the C2CZeolite Corporation of Calgary, Canada. In some embodiments, the zeolitemay be present in the plugging compositions of the present invention inan amount in the range of about 5% to about 65% by weight ofcementitious components. In certain embodiments, the zeolite may bepresent in an amount in the range of about 10% to about 40% by weight ofcementitious components. One of ordinary skill in the art, with thebenefit of this disclosure, will recognize the appropriate amount of thezeolite to include for a chosen application.

Embodiments of the plugging compositions further may comprise a setretarding additive. As used herein, the term “set retarding additive”refers to an additive that retards the setting of the pluggingcompositions of the present invention. Examples of suitable setretarding additives include, but are not limited to, ammonium, alkalimetals, alkaline earth metals, metal salts of sulfoalkylated lignins,organic acids (e.g., hydroxycarboxy acids), copolymers that compriseacrylic acid or maleic acid, and combinations thereof. One example of asuitable sulfoalkylated lignin comprises a sulfomethylated lignin.Suitable set retarding additives are disclosed in more detail in U.S.Pat. No. Re. 31,190, the entire disclosure of which is incorporatedherein by reference. Suitable set retarding additives are commerciallyavailable from Halliburton Energy Services, Inc. under the trademarksHR® 4, HR® 5, HR® 7, HR® 12, HR®15, HR®25, HR®601, SCR™ 100, and SCR™500 retarders. Generally, where used, the set retarding additive may beincluded in the plugging compositions of the present invention in anamount sufficient to provide the desired set retardation. In someembodiments, the set retarding additive may be present in the pluggingcompositions of the present invention an amount in the range of about0.1% to about 5% by weight of cementitious components. One of ordinaryskill in the art, with the benefit of this disclosure, will recognizethe appropriate amount of the set retarding additive to include for achosen application.

Optionally, other additional additives may be added to the pluggingcompositions of the present invention as deemed appropriate by oneskilled in the art, with the benefit of this disclosure. Examples ofsuch additives include, but are not limited to, strength-retrogressionadditives, set accelerators, weighting agents, lightweight additives,gas-generating additives, mechanical property enhancing additives,lost-circulation materials, filtration-control additives, dispersants,fluid loss control additives, defoaming agents, foaming agents,oil-swellable particles, water-swellable particles, thixotropicadditives, and combinations thereof. Specific examples of these, andother, additives include crystalline silica, amorphous silica, fumedsilica, salts, fibers, hydratable clays, microspheres, rice husk ash,elastomers, elastomeric particles, resins, latex, combinations thereof,and the like. A person having ordinary skill in the art, with thebenefit of this disclosure, will readily be able to determine the typeand amount of additive useful for a particular application and desiredresult.

As will be appreciated by those of ordinary skill in the art,embodiments of the plugging compositions of the present invention may beused for forming a seal in a plug-and-abandon operation. An example of amethod for plugging and abandoning a well comprises placing a pluggingcomposition in a selected plug location in a well bore and allowing theplugging composition to set to form a plug. The plug location may beselected so that the well bore can be sealed off for abandonment. Forexample, the plug location may be selected so that selected interval ofthe well bore may be sealed. In an embodiment, the selected location maybe adjacent to a hydrocarbon-containing formation or a water-containingformation. In an embodiment, the plugging and abandoning operation mayinclude the formation of two or more plugs in the well bore. Forexample, the method may further include placement of a second pluggingcomposition in another selected plug location in the well bore.

To facilitate a better understanding of the present invention, thefollowing examples of certain aspects of some embodiments are given. Inno way should the following examples be read to limit, or define, thescope of the invention.

Example 1

A series of sample plugging compositions were prepared at roomtemperature and subjected to 24-hour crush strength tests at 185° F. inaccordance with API Specification 10 to determine force resistanceproperties of plugging compositions that comprise CKD, pumicite, andlime. The sample compositions were allowed to cure in a water bath at185° F. for twenty-four hours. Immediately after removal from the waterbath, crush strengths were determined using a Tinius Olsen tester. Theresults of the crush strength tests are set forth in the table below.

Each of the samples had a density of 12.5 ppg and contained 200-meshpumicite, Joppa CKD, lime, and water and were free of Portland cement.In the following table, percent by weight is based on the weight of thepumicite and the CKD in the samples.

TABLE 1 Crush Strength Tests: Pumicitc, CKD, and Lime 24-Hr CrushPumicite CKD Lime Strength Sample Water (gal/sk) (% by wt) (% by wt) (%by wt) (psi) 1 9.42 65 35 5 83.8 2 9.82 65 35 10 126.3 3 10.15 65 35 14229 4 9.33 70 30 5 75.6 5 9.74 70 30 10 358 6 10.06 70 30 14 182.6 79.25 75 25 5 52.8 8 9.65 75 25 10 314 9 9.98 75 25 14 147 10 9.16 80 205 32.1 11 9.57 80 20 10 305 12 9.89 80 20 14 144.8

Example 1 thus indicates that plugging compositions containing pumicite,CKD, and lime and essentially free of Portland cement may haveproperties suitable for use in plug-and-abandon operations.

Example 2

An additional series of sample plugging compositions were prepared andtested to determine to further analyze the force resistance propertiesof plugging compositions that comprise CKD, pumicite, and lime. Thesamples were prepared and allowed to cure in a water bath at 140° F. Thetwenty-four hour and seventh-two hour crush strengths were determined at140° F. using a Tinius Olson tester in accordance with API Specification10. The results of the crush strength tests are set forth in the tablebelow.

Each of the samples had a density of 15 ppg and comprised Portland ClassH cement, Joppa CKD, 200-mesh pumicite, hydrated lime, a dispersant(CFR™-3 cement friction reducer), and/or water, as indicated in thetable below. In the following table, percent by weight is based on theweight of the pumicite and the CKD for Samples 13-21 and on the Portlandcement for Sample 22.

TABLE 2 Crush Strength Tests: Pumicite, CKD, and Lime 24-Hr 72-HrPortland Hydrated Crush Crush Cement CKD Pumicite Lime DispersantStrength Strength Sample (% by wt) (% by wt) (% by wt) (% by wt) (% bywt) (psi) (psi) 13 — 90 10 5 0.75 306 1209 14 — 75 25 5 1 514 1988 15 —75 25 10 1 520 1673 16 — 50 50 5 1.25 876 2180 17 — 50 50 10 1.25 13522280 18 — 25 75 5 1.5 896 1402 19 — 25 75 10 1.5 1674 1850 20 — 100 0 01 200 520 21 — 0 100 10 2 812 1261 22 100 — — — — 1202 2460

Example 2 thus indicates that plugging compositions containing pumicite,CKD, and lime and essentially free of Portland cement may haveproperties suitable for use in plug-and-abandon operations.

Example 3

An additional series of sample plugging compositions were prepared andtested to determine to further analyze plugging compositions thatcomprise CKD, pumicite, and lime. The samples were prepared and allowedto cure in a water bath at 140° F. The crush strengths were determinedat forty-eight hours and 160° F. using a Tinius Olson tester inaccordance with API Specification 10. The thickening time for eachsample was also determined at 140° F. in accordance with APISpecification 10.

Each of the samples had a density of 14 ppg and comprised Portland ClassH cement, silica (Silicalite™ cement additive), Joppa CKD, 200-meshpumicite, hydrated lime, a dispersant (CFR™-3 cement friction reducer),a cement set retarder (HR®-5 cement retarder), and/or water, asindicated in the table below. In the following table, percent by weightis based on the weight of the pumicite and the CKD for Samples 23-26 andon the Portland cement for Sample 27.

TABLE 3 Crush Strength Tests: Pumicite, CKD, and Lime Portland HydratedThickening 48-Hr Cement Silica CKD Pumicite Lime Set Time Crush (% by (%by (% by (% by (% by Dispersant Retarder to 70 bc Strength Sample wt)wt) wt) wt) wt) (% by wt) (% by wt) (psi) (psi) 23 — — 75 25 5 1 1 6:021013 24 — — 50 50 5 1 0.7 5:36 1701 25 — — 50 50 10 1.25 0.75 5:23 171726 — — 25 75 10 1.75 0.4 4:41 1523 27 100 8 — — — — 0.4 5:47 2040

Example 3 thus indicates that plugging compositions containing pumicite,CKD, and lime and essentially free of Portland cement may haveproperties suitable for use in plug-and-abandon operations.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Although individual embodiments arediscussed, the invention covers all combinations of all thoseembodiments. Furthermore, no limitations are intended to the details ofconstruction or design herein shown, other than as described in theclaims below. It is therefore evident that the particular illustrativeembodiments disclosed above may be altered or modified and all suchvariations are considered within the scope and spirit of the presentinvention. While compositions and methods are described in terms of“comprising,” “containing,” or “including” various components or steps,the compositions and methods can also “consist essentially of” or“consist of” the various components and steps. Whenever a numericalrange with a lower limit and an upper limit is disclosed, any number andany included range falling within the range is specifically disclosed.In particular, every range of values (of the form, “from about a toabout b,” or, equivalently, “from approximately a to b,” or,equivalently, “from approximately a-b”) disclosed herein is to beunderstood to set forth every number and range encompassed within thebroader range of values. Also, the terms in the claims have their plain,ordinary meaning unless otherwise explicitly and clearly defined by thepatentee.

1. A method of plugging a well bore for abandonment comprising: placinga plugging composition in the well bore, the plugging compositioncomprising: cement kiln dust in an amount of about 5% to about 100% byweight of cementitious components, pumicite in an amount of about 5% toabout 100% by weight of cementitious components, 0% to about 24% ofPortland cement by weight of cementitious components, and water; andallowing the plugging composition to set and form a plug.
 2. The methodof claim 1 wherein the plugging composition has a density of about 8pounds per gallon to about 16 pounds per gallon.
 3. The method of claim1 wherein the cement kiln dust is present in an amount of about 25% toabout 75% by weight of cementitious components, and wherein the pumiciteis present in an amount of about 25% to about 75% by weight ofcementitious components.
 4. The method of claim 1 wherein the watercomprises at least one water selected from the group consisting offreshwater, saltwater, brine, seawater, and any combination thereof. 5.The method of claim 1 wherein the water is present in an amount of about40% to about 200% by weight of cementitious components.
 6. The method ofclaim 1 wherein the plugging composition further comprises lime.
 7. Themethod of claim 1 wherein the plugging composition further compriseshydrated lime in an amount of about 1% to about 40% by weight ofcementitious components.
 8. The method of claim 1 wherein the pluggingcomposition comprises 0% to about 1% of Portland cement by weight ofcementitious components.
 9. The method of claim 1 wherein the pluggingcomposition further comprises at least one additive selected from thegroup consisting of fly ash, slag cement, metakaolin, shale, zeolite,crystalline silica, amorphous silica, fumed silica, salt, fiber,hydratable clay, microsphere, rice husk ash, elastomer, elastomericparticle, resin, latex, and any combination thereof.
 10. The method ofclaim 1 wherein the plugging composition further comprises at least oneadditive selected from the group consisting of a set retarding additive,a strength-retrogression additive, a set accelerator, a weighting agent,a lightweight additive, a gas-generating additive, a mechanical propertyenhancing additive, a lost-circulation material, a filtration-controladditive, a dispersant, a fluid loss control additive, a defoamingagent, a foaming agent, an oil-swellable particle, a water-swellableparticle, a thixotropic additive, and any combination thereof.
 11. Themethod of claim 1 further comprising forming a second plug in thesubterranean formation using a plugging composition comprising cementkiln dust and pumicite.
 12. A method of plugging a well bore forabandonment comprising: placing a plugging composition in the well bore,the plugging composition comprising: a cementitious component consistingessentially of cement kiln dust, pumicite, and lime, and water; andallowing the plugging composition to set and form a plug.
 13. The methodof claim 12 wherein the plugging composition has a density of about 8pounds per gallon to about 16 pounds per gallon.
 14. The method of claim12 wherein the cement kiln dust is present in an amount of about 25% toabout 75% by weight of cementitious components, and wherein the pumiciteis present in an amount of about 25% to about 75% by weight ofcementitious components.
 15. The method of claim 12 wherein the watercomprises at least one water selected from the group consisting offreshwater, saltwater, brine, seawater, and any combination thereof. 16.The method of claim 12 wherein the lime comprises hydrated lime, thehydrated lime present in an amount of about 1% to about 40% by weight ofcementitious components.
 17. The method of claim 12 wherein the pluggingcomposition further comprises at least one additive selected from thegroup consisting of zeolite, crystalline silica, amorphous silica, fumedsilica, salt, fiber, hydratable clay, microsphere, rice husk ash,elastomer, elastomeric particle, resin, latex, and any combinationthereof.
 18. The method of claim 12 wherein the plugging compositionfurther comprises at least one additive selected from the groupconsisting of a set retarding additive, a strength-retrogressionadditive, a set accelerator, a weighting agent, a lightweight additive,a gas-generating additive, a mechanical property enhancing additive, alost-circulation material, a filtration-control additive, a dispersant,a fluid loss control additive, a defoaming agent, a foaming agent, anoil-swellable particle, a water-swellable particle, a thixotropicadditive, and any combination thereof.
 19. The method of claim 12further comprising forming a second plug in the subterranean formationusing a plugging composition comprising cement kiln dust and pumicite.20. A plugging composition comprising: cement kiln dust in an amount ofabout 5% to about 100% by weight of cementitious components; pumicite inan amount of about 5% to about 100% by weight of cementitiouscomponents; 0% to about 24% of Portland cement by weight of cementitiouscomponents; and water.